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1、BRITISH STANDARD BS 2494:1990 Implementing Amendment No. 1 not published separately Specification for Elastomeric seals for joints in pipework and pipelines ICS 23.040.80 Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:55:43 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2494:1990 This Brit
2、ish Standard, having been prepared under the direction of the Rubber Standards Policy Committee, was published under the authority of the Board of BSI and comes into effect on 31 August 1990 BSI 07-1999 BS 2494-1 First published November 1975 BS 2494-2 First published December 1967 Second edition, a
3、s BS 2494, February 1976 Third edition March 1986 Fourth edition August 1990 The following BSI references relate to the work on this standard: Committee reference RUM/1 Draft for comment 89/43852 DC ISBN 0 580 18808 6 Committees responsible for this British Standard The preparation of this British S
4、tandard was entrusted by the Rubber Standards Policy Committee (RUM/-) to Technical Committee RUM/1, upon which the following bodies were represented: British Gas Corporation British Plastics Federation British Precast Concrete Federation Ltd. British Rubber Manufacturers Association British Steel I
5、ndustry Clay Pipe Development Association Ltd. Ductile Iron Producers Association Engineering Equipment and Materials Users Association Fibre Cement Manufacturers Association Ltd. Institution of Gas Engineers Institution of Production Engineers Institution of Water Engineers and Scientists Malaysian
6、 Rubber Producers Research Association Ministry of Defence Rubber and Plastics Research Association of Great Britain Water Authorities Association Water Companies Association Water Research Centre Amendments issued since publication Amd. No.Date of issueComments 9262December 1997 Indicated by a side
7、line in the margin Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:55:43 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2494:1990 BSI 07-1999i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Designation1 3General1 4Text deleted3 5Text deleted3 6Seals of type T (ab
8、ove ground drainage)3 7Seals of type G (gas and hydrocarbon fluids)3 8Text deleted3 Appendix A Method of tensile testing for spliced joints7 Appendix B Text deleted7 Appendix C Alternative tensile test piece7 Appendix D Method for measurement of low temperature hardness change7 Appendix E Method for
9、 determining resistance to liquid immersion and desorption8 Appendix F Method for assessing the integrity of moulded seals of type T8 Appendix G Recommendations for storage of seals8 Figure 1 Mould lay out for sample plates6 Figure 4 Dimensions of alternative dumb-bell 7 Table 1 Designation of elast
10、omeric joint seals by type and application2 Table 2 Flash size2 Table 5 Physical properties for seals of type T (thermoplastic elastomers for above ground use only)4 Table 6 Physical properties for seals of type G (gas and hydrocarbon fluids)5 Table 8 Sustained extension for splice joints7 Publicati
11、ons referred toInside back cover Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:55:43 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2494:1990 ii BSI 07-1999 Foreword This British Standard has been prepared under the direction of the Rubber Standards Policy Committee and supersedes BS 2494
12、:1986, which is withdrawn. BS EN 681-1 contains requirements that supersede those for types W, D, H and S in BS 2494:1990. BS EN 681-2, to be published shortly, will supersede requirements for Type T. BS EN 682, when published, will supersede requirements for Type G. NOTEThe manner in which seals ar
13、e stored between manufacture and use is most important and it is recommended that the advice given in Appendix G is followed. It has been assumed in the drafting of this British Standard that the execution of its provisions is entrusted to appropriately qualified and experienced personnel. To assure
14、 themselves that products claimed to comply with BS 2494 consistently achieve the required level of quality, purchasers ordering to this standard are advised to specify in their purchasing contract that the supplier operates a quality system in compliance with BS 5750-2. WARNING. This standard calls
15、 for the use of substances and/or procedures that may be injurious to health if adequate precautions are not taken. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a B
16、ritish Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 to 8, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendmen
17、ts incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:55:43 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2494:1990 BSI 07-19991 1 Scope This British Standard specifies performance requirements and gives me
18、thods of test for one type of elastometric joint seal made of thermosetting elastomeric compounds and one type of joint seal made of thermoplastic elastomeric compounds (see clause 2) and the compounds from which they are manufactured. It is applicable to elastomeric components of composite or non-c
19、omposite rings, seals, jointing gaskets, and similar components used to seal fluids in pipes and fittings. Other requirements for the performance of the finished joint seals, particularly functional tests for the performance of the actual sealing systems used with particular pipeline materials, are
20、specified in appropriate British Standards. Methods of test are given in Appendix A and Appendix C to Appendix F. Recommendations for the storage of seals are given in Appendix G. NOTEThe titles of the publications referred to in this standard are listed on the inside back cover. 2 Designation Elast
21、omeric joint seals shall be designated according to their intended application as given in Table 1. 3 General 3.1 Materials Seals of thermosetting elastomers shall be manufactured from compounds that are free from reclaimed rubber, vegetable oils, factice and vulcanized waste. Seals of type T shall
22、be manufactured from material that consists substantially of thermoplastic elastomers to which may be added only those additives necessary for their manufacture and processing into sound durable mouldings. These seals may also contain the manufacturers own clean rework material resulting from the ma
23、nufacture of seals to this standard. No other rework material shall be used. 3.2 Hardness Seals shall be classified in two different hardness ranges, as given in Table 5 and Table 6. When measured in accordance with the microtest described in BS 903-A26, the hardness shall not differ by more than 3
24、IRHD from the specified nominal value. NOTE 1It is common commercial practice for the seal hardness to be specified by the purchaser. NOTE 2Although BS 903-A26 states that the microtest is preferably for use in the hardness range 30 IRHD to 85 IRHD, for application to joint seals it is considered to
25、 be suitable for measurements up to 91 IRHD. 3.3 Appearance and finish The seals shall be smooth and free from air marks and other blemishes. The elastomeric material forming the seals shall be homogeneous and free from porosity, as judged without magnification, on the surface or on any cut section.
26、 If a seal exhibits flash, it shall not impair the sealing properties of the seal. Flash shall be kept to a minimum and neither the thickness nor the width of the flash shall exceed the values given in Table 2 relative to the nominal dimension of the seal section. 3.4 Dimensional tolerances The tole
27、rances on dimensions of finished seals shall be in accordance with class M2 of BS 3734 for moulded products and class E1 of BS 3734 for extruded products. The tolerance on the diameter of seals made from cut and jointed lengths of vulcanized material shall be in accordance with class M2 of BS 3734.
28、3.5 Splice joined seals 3.5.1 Materials. Any materials used to assist in making splice joints shall not detract from the performance of the seal type concerned. 3.5.2 Strength. There shall be no visible separation in the area of the splice when a jointed seal or linear test piece is tested as descri
29、bed in Appendix A. 3.6 Moulding integrity (weld lines and gatemarks) When tested in accordance with Appendix F injection moulded seals of the type T, gated so as to produce a weld line, shall not exhibit damage resulting from the elongation when examined in good light, without magnification. 3.7 Com
30、posite seals Each elastomeric component of a composite seal shall comply with all the other requirements of this standard for the corresponding type of seal designated in Table 1, except for those components that will not be exposed to the contents of the pipeline or pipework. NOTEDifferent elastome
31、ric components of a composite seal may be selected from different hardness ranges. Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:55:43 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 2494:1990 2 BSI 07-1999 Table 1 Designation of elastomeric joint seals by type and application Table 2 Flas
32、h size 3.8 Quality assurance NOTEFor advice on quality systems see foreword. 3.8.1 Type tests. All tests for the appropriate designation of seal shall be carried out at least annually and whenever the manufacturing technique is changed. All tests, without exception, shall also be carried out wheneve
33、r the elastomer formulation is changed. All of these tests shall either be carried out using test pieces cut from the finished seals or, if the shape of the seal does not permit test pieces to be produced, on laboratory samples of the same formulation, and same state of cure and method of preparatio
34、n as the finished seals in the case of thermosetting elastomeric compounds and the same moulding conditions in the case of thermoplastic materials. For tests in which different sizes of test pieces are permissible, the same size of test piece shall be used for each batch (see 3.8.3) and for any comp
35、arative purposes. In the case of thermoplastic materials test pieces shall be taken from the same mould for comparative purposes. Directions in which dumb-bells shall be cut are indicated in either Figure 1(a) or Figure 1(b). 3.8.2 Product control tests. The following tests shall be carried out acco
36、rding to the conditions listed in the appropriate Table 5 and Table 6, using test pieces in accordance with 3.8.1, obtained as specified in 3.8.3: a) tensile strength; b) elongation at break; c) compression set, 22 h at 70 C for types W, D and G, 22 h at 125 C for types H and S or 70 h at 23 C for t
37、ype T; d) hardness; e) splice strength (where applicable), see 3.5; f) moulding integrity for type T where applicable. 3.8.3 Sampling for product control tests. The product control tests shall be carried out on batches of finished components using sampling procedures in accordance with either: a) BS
38、 6001 with a specified inspection level of S 2 and an AQL of 2.5 % for attributes; or b) BS 6002 with a specified inspection level of S 3 and an AQL of 2.5 % for variables. NOTEThese requirements do not preclude the use by the manufacturer of more stringent combination of inspection levels and AQL v
39、alues from BS 6001 or BS 6002. 3.9 Marking Each seal shall be marked clearly and durably with the following information in a manner that does not interfere with the sealing function of the seal. a) The nominal size. NOTE 1Joint seals are generally characterized by a nominal size defined not by this
40、specification but by the pipework pipeline or joint system indicated by the manufacturer as that for which the particular size and shape of seal is designed. b) The manufacturers identification. c) The number of this British Standard, i.e. BS 2494:1990 with the seal type designation (see clause 2) a
41、s a suffix, with or without inclusion of the date of this standard, e.g. “BS 2494:1990: G” or “BS 2494: I” d) The quarter and year of manufacture. TypeIntended application T(drainage)Thermoplastic rubbers for above ground drainage only G(gas and hydrocarbon fluids)Town gas and other hydrocarbon gase
42、s as described in Appendix B of BS 1179:1967 or in BS 4250 or 1st and 2nd family gases as defined in BS 4947. Hydrocarbon fluids with an aromatic content of not more than 30 %, and not including edible oils Nominal dimensions of seal section Maximum flash thickness and/or width Flash size designatio
43、na mm u 5 5 to 10 10 to 16 16 to 25 25 to 40 40 to 65 65 mm 0.10 0.20 0.40 0.50 0.60 0.70 0.80 F.1 F.2 F.3 F.4 F.5 F.6 F.7 a These designations are for guidance only and may be referred to by joint seal designers. Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:55:43 GMT+00:00 2006, Uncont
44、rolled Copy, (c) BSI BS 2494:1990 BSI 07-19993 NOTE 2The following information is also desirable: 1) the British Standard abbreviation for the elastomer used (see BS 3502-3 where applicable); 2) the type of joint for which the seal is intended. In cases where marking the actual component is not prac
45、ticable (e.g. when sections are too small), seals shall be supplied in parcels and each parcel shall be marked with the above information. In such cases, every seal shall carry the manufacturers identification unless this interferes with the sealing function. 4 Text deleted 5 Text deleted 6 Seals of
46、 type T (above ground drainage) The physical properties of type T seals shall be as given in Table 5. 7 Seals of type G (gas and hydrocarbon fluids) The physical properties of type G seals shall be as given in Table 6. 8 Text deleted Licensed Copy: sheffieldun sheffieldun, na, Tue Nov 28 13:55:43 GM
47、T+00:00 2006, Uncontrolled Copy, (c) BSI BS 2494:1990 4 BSI 07-1999 Table 5 Physical properties for seals of type T (thermoplastic elastomers for above ground use only) PropertyUnitTest methodTest piece (see 3.8) Hardness range 36 to 4546 to 5556 to 6566 to 75 Tensile strength, min.MPaBS 903:A2BS 90
48、3:A2 type 2 or as in Appendix Ca 4446 Elongation at break, min.%BS 903:A2As above400375300300 Hardness (microtest)IRHDBS 903:A262 mm minimum thicknessa Within 3 of specified hardness Compression set, max., 23 C, 70 h%BS 903:A6BS 903:A6 type 1 or 25252525 70 C, 22 h5 mm dia. 3.5 mm or 7 mm dia. 3.5a
49、40404040 Stress relaxation, max.%BS 903:A42 23 C BS 903:A42 type 1 15202525 Water absorption, swell, max.%BS 903:A16 volumetric method, 70 C, 168 h As specified6666 Low temperature hardness change, max. from 23 C value (normal test) IRHDAppendix D 0 C, 70 h As specifieda5555 Ozone testBS 903:A43: procedure A,5 % strain, 30 C, 24 h, 10 5 p.p.h.m. ozoneb, 55 5 % r.h. As specifiedNo cracking visible under 7 magnification Accelerated ageing 70 C, 168 hBS 903:A19: method A or Bc Tensile strength, max. change from original %BS 903: